Subject: Re: Bug: timer going backward on a dual core
From: john stultz <johnstul@us.ibm.com>
To: Claudio Scordino <cloud.of.andor@gmail.com>
Cc: kernelnewbies@nl.linux.org, linux-kernel@vger.kernel.org
In-Reply-To: <200510282227.36433.cloud.of.andor@gmail.com>
References: <200510282109.42054.cloud.of.andor@gmail.com>
	 <1130527831.27168.413.camel@cog.beaverton.ibm.com>
	 <200510282227.36433.cloud.of.andor@gmail.com>
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Date: Fri, 28 Oct 2005 13:43:31 -0700
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On Fri, 2005-10-28 at 22:27 +0200, Claudio Scordino wrote:
> > > We have a dual-core AMD64 with the new kernel 2.6.14 and the
> > > timer goes backward...
> > >
> > >
> > > CONFIGURATION:
> > >
> > > Kernel: 2.6.14
> > > Distribution: Gentoo Linux 2005.0
> > > Processor: Athlon 64 x2 4200+ (dual core)
> > > Motherboard: Abit KN8
> > > Memory: 1GB PC3200
> > >
> > >
> > > PROBLEM:
> > >
> > > gettimeofday goes backward and returns values that are not monotonic,
> > > giving values that are smaller than values returned before.
> > >
> > > The system has been tested with timer as PIT, PIT/TSC and PM and the
> > > problem occurs with all the configurations.
> > >
> > > Here is the config file that we used for the PM configuration.
> > >
> > > Any suggestion ?
> >
> > Booting w/ idle=poll tends to work around this issue. You might check
> > with your motherboard vendor for an updated BIOS that supports HPET or
> > the ACPI PM timer.
> 
> We already updated the BIOS with the latest version.
> 
> Also the booting command idle=poll doesn't work.


Hmm. Not sure then. Is this a new regression on the same hardware?

Also, how are you measuring time going backwards?

Would you mind filing a bug (http://bugzilla.kernel.org )on this and
attaching your config and dmesg there? 


thanks
-john

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